DC Block Wiring - SPST or DPDT switches?

Model Railroader Electronics and DCC
1

I got a great deal on a bulk supply of switches so I bought a bunch of great toggle switches that are just on and off. No middle position.

Does it matter which type I use? I cant seem to get a clear discussion of that topic.

I am wiring blocks in my 4x8 layout and thought all i need to do it turn power on or off to each block.

Please enlighten me :slight_smile:

2

If you are only using one pack, they will allow you to park or power down engines in each block.

If you want to use more than one power pack they will not work. You need the center off pole switch as shown:

3

Sensei,

Please tell me more. I want to use more than one power pack. so the center off switch is needed, why do i need power on-off-on feature of the switch?

thanks,

Grasshoper

4

The center off position allows you to park engines anywhere on the layout and still use both power packs elsewhere.

5

You can also use DPDT switches. The difference is that there would not be a “common” wire. There would be two wires from each switch to each section of track. And two wires from each power pack to each switch.

6

Ok what does it mean if I don’t have a common wire?

7

KGILL,

Look at SOO,Lines diagram,study it,then read TZ’s response,your answer for your question,has already been explained…

Cheers,

Frank

8

Side note: I actually prefer DPDT, since it allows for complete circuit isolation. While i know that SPDT + common wire allows for lower overall costs, it does present a bit of a complicating factor when troubleshooting a short comes into play.

To the OP though: Lacking center off may be an issue if switches are the “make-before-break” type. This could cause a power pack to power pack short :confused:

If the switches are “break-before-make” type, then you can over come the lack of center off by using one of the switches as an ON/OFF for the block, and then a second switch for the CAB select.

I’m away from my home computer or I’d whip up a quick schematic.

Cheers!

9

Actually there is a third option. One can use the common wire arrangement and just use 1/2 of the DPDT switch, in effect making it a SPDT.

10

Here is a diagram using Atlas Selectors:

11

Jim, your diagrams are terrific! Nice of you to take the trouble to so clearly illustrate the systems. Pic’s are worth 1K words.

12

Paul,

Thanks for the kind words. They were done using a program called Visio professional.

13

Jim, PLEASE change the turnout to place the short rail ABOVE the longer one so that any car or engine’s wheels could actually be routed to the side track. Thanks, JWH